I got yellow ingots a long time ago. So long that I had quite forgot about it until you mentioned it in your post.
I never knew what caused it. I never did anything special to make it go away.
But I was less than careful with my lead sources in those days. I even melted down old lead acid batteries.
I came up with a large supply of pure lead and the ingots started casting pretty nice and silvery.
I think there are couple of things that are important in your lead for BP. It should be soft enough to take the rifling. This means at least some level of purity.
TEST - Try to groove the ingot or the ball with your thumb nail. If you can, the hardness is right and you have at least minimal purity. Others in the group...Please review my comments and correct as needed.
The cast bullets should have good internal homogeneity. No voids, no areas of amalgamations of other substances which might throw off the balance of the projectile making it inaccurate as the rifling imparts a spin.
TEST - Shoot them. Bad internal homogeneity will manifest itself in large groups on a bench rest.
It should also be free of substances which harm the bore. I have been told that enough of the caustic character remains in battery lead (aside from the fact that it is not pure lead) that bullets cast from it will corrode the barrel quickly.
NO TEST - If you suspect such impurities, clean often and clean well.
A projectile made of pure lead will have a specific weight. I worked out the weights of pure lead balls of various diameters a while back but I have lost the calculations and can't remember what they are. Since you can't trust that a .454 mold will produce a consistent .454 ball, I worked out the calculations for every thing from a .451 to a .459. The calculations are quite simple but they are tedious. I wish I still had them, because when I worked them up, I remember comparing them with the projectile weights from the Lyman Handbook and found that the Lyman book published weights that were slightly less than my calculations for pure lead in every case. This means that the Lyman bullets were likely not pure IF THEY ACTUALLY WEIGHED THE BULLETS. And I think they did.
TEST - Measure the diameter of your roundballs. Weigh them with an accurate scale. compare the weight you measure with the weight you calculate. The purer your cast roundballs are, the closer to the ideal weight they will be.
Balls bought from a store or cast from molds at home are not perfectly spherical. Before this post I did some measurements on the round balls I have in my shooting box. I took six balls I had cast myself and six balls from Hornady. Then I measured the diameters on the balls in six different places. (Six diamters for each ball.) I used a Starret one inch micrometer. I got a range of measurements on my cast balls of .0015. On the Hornady balls, I got .003. About twice the range.
When you ram the ball, you change it from a sphere to essentially a very short cylinder with profoundly rounded ends, front and back. When the ball passes down the bore of the barrel it changes shape once more.
I can get fairly descent accuracy from both cast balls and bought balls, so my thought is that a lot of the things I have mentioned are not very important. I bench rest most of my shots because 1) I am not much of an off hand shot and 2) that is the way I want to shoot.
My reading of history convinces me that most bad government results from too much government. Thomas Jefferson
Last edited by Doc Hoy; September 25, 2010 at 06:05 PM.